The present invention relates to a propeller shaft, for instance, for a vehicle, and also relates to a yoke structure of a universal joint used for the propeller shaft.
As a related art propeller shaft, Japanese Patent Provisional Publication No. 2008-208919 (hereinafter is referred to as “JP2008-208919”) discloses the propeller shaft.
As is known in the art, this propeller shaft is a propeller shaft that transmits a driving force of an engine, which is outputted from a transmission mounted on a front side of a vehicle, to a differential gear mounted on a rear side of the vehicle. The propeller shaft and the transmission are coupled together by the fact that a yoke of a universal joint provided at a front end portion of the propeller shaft and a connecting member provided at a top end portion of an output shaft of the transmission are connected by tightening of bolt and nut.
The yoke has a substantially rectangular mounting flange in which four bolt insertion holes are formed at four corners and has a pair of yoke portions having a bifurcated shape which protrude from one side surface of the mounting flange. On the other hand, the connecting member has a substantially circular flange portion that is made abut on or touches the mounting flange from an axial direction. Four bolts, e.g. four stud bolts, which are inserted into the four bolt insertion holes are fixed to this flange portion at four points in a circumferential direction of the flange portion. The yoke of the propeller shaft and the connecting member of the output shaft of the transmission are connected, through the mounting flange of the yoke and the flange portion of the connecting member, by screwing the nut onto the stud bolt and tightening it using a turning tool (a tightening tool), e.g. a socket wrench.